Saponification of cellulose ester material



Patented Sept. 7, 1937 UNITED STATES SAPONIFICATION 0F CEDLULOSE ESTERMATERIAL Robert Wighton Moncrleif, Frank Brentnall Hill, and ThomasBarnard Frearson, Spondon, near Derby, England, assignors to CelaneseCorporation of America, a corporation of Delaware No Drawing.Application December'ii, 1934, Se-

rial No. 756,284. ,In Great Britain December 12 Claims.

This invention relates to the treatment 01' cel-- lulose acetate andother organic esters of cellulose and particularly to a process forreducing the acidyl content of such esters. The invention 5 is speciallyapplicable to the saponification of filaments, threads, yarns, ribbonsand the like made of or containing such esters.

It has been discovered that organic esters .of cellulose can besaponified by means of nonmetallic bases, for example methylamine,ethylene diamine and other aliphatic amines, particularly those of lowmolecular weight in the liquid phase, with particular advantage and thatby treating threads of cellulose acetate and like materials in this wayspeciallydesirable proper ties maybe imparted to' the materials. We havenow found that the 'saponification of materials having a basis ofcellulose acetate or other or- .ganic ester of cellulose by means ofnon-metallic saponifying agents and in particular methylamine andsimilar bases may be accelerated to a considerable extent by thepresence during the saponification of heavy metals, 1. e. metals otherthan the alkali and alkaline earth metals.

It is to be understood that the term metal is used in a sense broadenough to include compounds of the metal. It appears that the metalswhich are most suitable for use in the process of lic bases is claimedin our co-pending U. S. appli-.

cation S. No. 756,285 filed December 6, 1934.

The metal is preferably added to the saponifying bath in the form of'asoluble salt but may also be employed in other forms, forexample in somecases it is convenient to add the metal in the form of an oxide orhydroxide. Preferably the metal is added in such a form that it readilydissolves in the saponifying bath, and the saponitying bath may as aresult contain a double, compound of the metal with the particular baseemployed. The saponifying bath may contain two or more heavy metalscapable of accelerating the saponification. Other accelerating agentsmay also be present, for example small quantities 01' caustic soda orother strong mineral base, as 'claimed in our co-pending U. S.application S.

No; 756,282, filed December 6, 1934.

The organic ester of cellulose treated may be of normal or lowviscosity, for example in the case of cellulose acetate the viscositymay be of the order of 30 to 50, 100, 200 or even higher, these figuresbeing obtained by comparison of a 6% solution of the ester in acetone at25 C. with glycerlneat the same temperature taken as a standard of 100.Such esters of'high viscosity may readily be made by methods'in whichdegradation of the cellulosemolecule is substantially avoided duringacidylation, for example-f the methods of U. S. .Patent No. 1,708,787.0n the other hand, the viscosity of the cellulose acetate employed maybeer the order of 10-20 or even lower, or between 20 and 30, measured onthe scale referred to above. v

The invention is of particular importance in connection with thesaponification of filaments, threads, ribbons, fabrics and likematerials having a basis of cellulose. acetate and will be describedwith special reference to the treatment of such materials.

The materials treated may be made by any suitable dry or wet spinningmethod. Where high tenacity is'required in the final products it is ofparticular advantage to produce the filaments andthe like by wetspinning methods in the.

course of which they are stretched to a considerf able extent, or tosoften and stretch the materials after their production whether by'a Wetor a dry spinning process. By applying the process of the invention tomaterials which have been stretched considerably, for example to 200%of'their original length or even more, materials of particularlyvaluable serimetric properties are obtainable.-

Particularly good results are obtained by the use of saponifying bathscontaining methyl- ,amine or ethylene diamine and silver, nickel orzinc. Other strong aliphatic organic bases, for example ethylamine,propylamine, amylamine and triethylamine, may also be employed,- Again,somewhat weaker bases of the same series, for example trimethylamine andallylamine, may be used. Further, considerably stronger bases of thesame series may be employed, even very strong bases such as tetramethylammonium hydroxide, provided carebe taken to avoid damaging thematerials. Again, amines other than ethylene diamine containing morethan one amino group, and particularly aliphatic diamines of relativelylow molecular weight, for

i example symmetrical dimethyl ethylene diamlne,

monomethyl ethylene diamine, and propylene diamine may also be used.Preferably at least one of the amino groups of such amines should beunsubstituted or mono-substituted. Amines containing more than two aminogroups may also be employed, for example 1.2.3-triamino propane. Theeifect of one or more hydroxy groups in the amine appears to be tofavour the penetration of the materials by the saponifying agent, andwith this object in view substances of the type ofwy-diaflliDO-fl-llYdl'OXY propane may be used with advantage. Again,bases of the heterocyclic series, for example piperidine.

may be used.

saponification is preferably effected by subjecting the materials to anaqueous bath containing methylamine or a like acting-base and the metalin solution. Generally speaking it is advantageous to employ the base ina concentration of 10-30%, and particularly 15-25%. The temperature ofthe bath may range from below atmospheric temperature to theneighbourhood of the boiling point of the solution. It is oftenconvenient to work at temperatures between 15 or 20 C. and 25 or 30 C.but when a high degree of saponification is to be effected it ispreferable to work at a somewhat higher temperature, e. g. -60 C. or 70C. or even higher, depending on the boiling point of the solution. Witha view to preventing excessive evaporation of the base it is ofadvantage, particularly when working at relatively high temperatures, tocover the surface of the saponifying bath with a layer of an oil, wax orlike substance which is immiscible with the bath. The concentrations andtemperatures employed in particular cases will naturally depend upon theproperties of the particular base employed. In general, the conditionsmay be chosen so that the desired degree of saponification may beeffected by means of a treatment lasting from 1-2 minutes or less up to3 or 4 minutes. On the other hand the treatment may be more protracted.

When the saponifying agent is applied to the materials in the form of anaqueous solution, it is convenient to incorporate the metal, for

. example in the form of the oxide or hydroxide or of a water-solublesalt, in the saponifying medium itself. It is not, however, essentialthat the metal should be introduced in this way. It may, for instance,be applied to the materials prior to the application of the saponifyingagent, or even introduced into the spinning solution from which they aremade.

A very considerable acceleration of the saponifying process may beeffected by the presence in the saponifying bath of quite smallconcentrations of the metal, e. g. 0.01-0.05% on the weight of the bathor even less. On the other hand somewhat higher concentrations may beemployed, e. g. 0.1% or 0.5%. Since it is undesirable that the finalproduct should contain substantial quantities of the metal it ispreferable to work with the smallest quantities capable of giving thedesired result.

The saponifying medium may also contain swelling agents, solvents orlatent solvents for the cellulose ester, for example cyclohexanol,methyl cyclohexanol, glycerol, ethylene glycol and its mono methyl anddimethyl ethers, diacetone alcohol, benzyl alcohol, acetone, dioxane ormethylene ethylene ether.

When the materials are treated in the form of filaments, threads, yarnsand the like, it is of adopted for this purpose.

advantage to effect saponification "in warp formation, i. e. by drawinga large number of ends through the bath in substantially parallelrelationship one to another and in the same plane.

Thus, yarn may be drawn from a creel by means of rollers or like devicesextending across the entire assembly of ends or so-called warp? andimmersed or partially immersed in a bath containing the saponifyingagent, through a reed into the bath, and after passing through the baththe materials may be drawn by a second roller, pair of rolls or thelike, situated outside the bath, through a reed and out of the bath,whence they are forwarded to suitable collecting means or to meansforeffecting any subsequent treatment to be applied. Preferably thematerials are washed and dried before being wound.

The saponifying agent may be applied by other means. Thus, for example,the materials in hank form may be suspended from rods which arecaused totraverse the length of the bath, and at the same time to rotate so as toexpose each portion of the yarn to the same depth in the bath for thesame period. Again, the materials may be treated in the form of bobbins,cheeses or other packages. Any suitable means may in fact be adopted inapplying the saponifying agent to the materials. Materials in yarn orlike form may be treated continuously with their production and/or witha stretching step. Again, in the case of such materials, stretching maybe effected during saponification or, provided saponification has notbeen carried too far, after saponification. In general it is necessaryto soften the materials to enable them to be stretched to the desiredextent, and in choosing a suitable softening agent due regard should behad to the extent to which the materials have been saponifled.

As indicated above, the materials may be saponifled in fabric form. Thismay conveniently be effected by passing the fabric continuously througha bath containing the saponifying agent, for example in an apparatus ofthe type of the winch dyeing machine.

It is generally advisable to treat the materials after saponificationso' as to remove any metal remaining therein. Any suitable means may beA convenient means comprises washing the materials with a dilute acidwith which the particular metal forms a soluble salt.

The materials prior to. saponification may be subjected to a treatmentadapted to facilitate penetration of the saponifying agent. This maycomprise the application of water to the materials, or they maybetreated with aqueous wetting agents, for example soaps.

The degree of saponification effected may be sufi'icient to reduce theacidyl content of the ester by 23-10% or even less, but is preferablysomewhat higher, for example suflicient to reduce the acidyl content by20-25% or 30%. Considerably higher degrees of saponification may beeffected sufficient to remove 35 or 40 to 50 or 55% of the acidylcontent or more, even up to complete saponification, according to theparticular purpose in view. Generally speaking, a loss in acidyl contentof 20-25 or 30% is capable of rendering the cellulose acetate materialinsoluble insoluble in substantially anhydrous acetone but may besoluble in acetone containing a considerable percentage, e. g. 25-30%,of water. Or saponiilcation may render the material insoluble in suchmixtures as well as in anhydrous acetone. The saponification may raisethe safe ironing point considerably. Materials saponifled according tothe invention may have, in addition to the valuable properties referredto above, a high tenacity and elasticity and a good extensibility.

Such materials are of particular value for use in the manufacture ofhigh twist yams. Thus, high twist yarns partially saponified accordingto the invention have been found particularly useful as weft in themanufacture of crepe fabrics. Again, by the process of the invention, itis possible to obtain completely saponified materials of excellenttensile properties.

The following examples illustrate the inve n-' tion:

Example 1 Cellulose acetate yarn is drawn in warp formation through anaqueous bath containing 15-30% of monomethylamine and 0.05-0.05% ofsilver, I I which is introduced into the bath in the form of silvernitrate. The temperature of the bath is maintained between 50 and 60 C.and the rate of travel of the materials is adjusted so that the yarn isin contact with the bath for 1-3 minutes.

Example 2 The process is carried out as described in-Example 1 exceptthat the bathcomprises a"'l5-30% aqueous solution of ethylene diaminecontaining 0.05-0.5% ofnickel which is introduced into the bath in theform of nickel sulphate.

Similarly other non-metallic bases, for example propylamine,di-methylamine or others of the bases referred to above may be applied.

Although the invention has been described with particular reference tothe treatment of materials having a basis of cellulose acetate, it isalso applicable to the treatment of othermaterials containing othersaponifiable esters of celluloss, for example cellulose formate,propionate, butyrate, ethyl cellulose acetate, oxy-ethyi celluloseacetate and nitrocellulose acetate.

What we calm and desire to secure by Letters Patent is:-- I

1. Process for reducing the acidyl content oi an organic ester ofcellulose, which comprisessaponii'ying the ester by means oi? asaponifying agent therefor which is a water-soluble nitrogenous organicbase in which each carbon atom that is directly attached to a nitrogenatom is directly attached to three other atoms apart from .said nitrogenatom, in the presence in solution of metal selected from the groupconsisting ct nickel, zinc, and silver.

2. Process for saponifying filaments, threads, ribbons and likematerials having a basis of organic ester 'of cellulose, which comprisestreating the materials with an aqueous solution of a 5 saponifying agenttherefor which is a water-soluble nitrogenous organic base in which eachcarbon atom that is directly attached to a nitrogen atom is directlyattached to three other atoms apart from said nitrogen atom, in thepresence in 7 solution of a metal selected from the group consisting ofnickel, zinc and silver.

3. Process for saponiiying filaments, threads.

, ribbons and like materials having a basis of cellulose acetate, whichcomprises treating the ma- 76 terials with an aqueous solution of asaponlfyins agent therefor which is a water-soluble"'nitrogenous organicbase in which each carbon atom that is directly attached to a nitrogenatom is I directly attached to three other atoms apart from saidnitrogen atom, in the presence in solution of a metal selected-from thegroup consisting of nickel, zinc and silver.

4. Process for saponifying illaments threads, ribbons and like materialshaving a basis of cellulose acetate, which comprises treating thematerials with an aqueous bath containing a watersoluble nitrogenousorganic base in which each carbon atom that is directly attached to anitrogen atom is directly attached to three other atoms apart from saidnitrogen atom which is a saponifying agent for the organic ester ofcellulose and a double compound of said base with a metal selected fromthe group consisting oi nickel,

zinc and silver.

5. Process for saponifying filaments, threads, ribbons and likematerials having a basis of organicester of cellulose, which comprisestreating the materials with an aqueous solution of a saponifying agenttherefor which is a water-soluble nitrogeneous organic base in whicheach carbon atom that is directly attached to a nitrogen atom isdirectly attached to three other atoms apart from said nitrogen'atom, inthe presence of nickel in solution. I

6. Process for saponifying filaments, threads, ribbons .and likematerials having a basis of organic ester ofceilulose, which comprisestreating the materials with an aqueous solution of a saponifying agenttherefor which is a watersoluble nitrogenous organic base in which eachcarbon atom that is directly attached to a nitrogen atom is directlyattached to three other atoms apart from said nitrogen atom, in thepresence of I atom is directly attached to three otheratoms apart fromsaid nitrogen atom, in the presence of silver in solution.

8. Process for saponifying filaments, threads,

ribbons and like materials having a basis of cellulose acetate, whichcomprises treating the materials with an aqueous solution of an amineselected from the group consisting of monomethylamine, mono-ethylamineand ethylene diamine, in the presence of nickel in solution.

9. Process for saponifying filaments, threads,

ribbons and like materialshaving a basis of cellulose acetate, whichcomprises treating the materials with an aqueous solution of an amineselected from the group consisting of monomethyiamine, mono-ethylamineand ethylene diamine, in the presence of zinc in solution.

10. Process for saponiiying filaments, threads, ribbons andlikematerials having a basis of cellulose acetate, which comprisestreating the materials with an aqueous-solution of an amine select .edfrom the group consisting of mono-methylamine, mono ethylamine andethylene diamine, in the presence 02 silver in solution.

11. Process for saponifyingdllaments, threads, ribbons and likematerials having a basis of organic ester of cellulose, which comprisestreating vthe materials with an aqueous medium contain-- in: in solutionan amine oi relatively low molecusolution anamine of relatively lowmolecular weight which is a saponifying agent for cellulose acetate anda metal selected from the group consisting ofnickel, zinc and silver.

ROBERT WIGHTON MONCRIEFF. FRANK BRENTNALL HILL. THOMAS BARNARD FREARSON.

